Reciprocating blade saw



United States Patent [72] inventors Gerald J. Shaw and William H. Hill,Shreveport, Louisiana [21] Appl. No. 757,739 [22] Filed Sept. 5, 1968[45] Patented Nov. 3, 1970 [73] Assignee Beaird-Poulan Inc.

Shreveport, Louisiana a corporation of Delaware [54] RECIPROCATING BLADESAW 5 Claims, 8 Drawing Figs.

[52] US. Cl 143/68, 310/166 [51] Int. Cl B27b 11/02 [50] Field of Search143/60- [56] References Cited UNITED STATES PATENTS 964,669 143/687/1910 Mayetal.

Primary Examiner- Donald R. Schran Attorney-Newton, Hopkins and OrmsbyABSTRACT: A gasoline engine driven reciprocating saw having an enginecrankshaft connected to the saw blade through a gearing and push rodarrangement. The components of the saw are arranged so that theprincipal movement of each component is along the central axis of thesaw which passes through the approximate center of gravity thereof. Oneof the gears of the gearing arrangement is connected to the saw blade bya first push rod to convert rotary motion into reciprocal motion and isconnected to a counterweight by another push rod. The push rods arearranged so that the saw blade and counterweight are always moving inthe opposite direction for the counterweight to counterbalance thevibrating action of the cutting blade and its associated components.

Patented Nov. 3, 19.70

Sheet INVENTORS GERALD J. SHAW \VILLIAIA BY Patented'fiqov. 3, 1970 wSheet 2 xwvsu'rons GERALD J. sHAw WILLIAM H. HILL BY Jim/on, mph),

1 RECIFROCA'IING BLADE SAW SPECIFICATION The present invention pertainsto saws generally, but more in particular to a gasoline engine drivensaw adapted to power a reciprocating blade for the purpose of cuttingwood.

While the present invention generally resembles a chain saw, ithas forone of its objects the provision of a cutting means, not in theconventional endless chain, but in a reciprocating blade with teethformed along one edge thereof.

Another object of the invention is the provision of a reciprocatingblade positioned along more-or-less the central longitudinal axis of thesaw to provide a convenient balance for an operator.

A further object of the invention is the provision of a gear train toreduce the reciprocatory movements of the cutting blade to a speedconsiderably less than the engine speed of the purpose of reducing wearand vibration.

There are three generally accepted forces in a device of this type whichcreate an unbalance:

1. ROTATING UNBALANCE-a force due to the weight of the large end of theconnecting rod and crankpin. This can be resolved or counterbalanced bythe use of counterweights on the crankshaft.

2. PRIMARY SHAKING FORCEresulting from the rapid starting and stoppingof the piston in its travel. This force is just as great as the rotatingunbalance and cannot be balanced out. Fortunately, however, it can begiven direction by over or under weighting of the crankshaftcounterweights.

. SECONDARY SHAKING FORCE-arising from the rapid back-and-forth pendulummotion of the connecting rod. Neither can this force be balanced out;but it is relatively small in comparison with the other forces.

In the present invention wherein a blade is made to reciprocate with itsassociated drive mechanism, there is yet another force of considerablevalue which must be balanced out if the full benefits of a blade cuttingsaw are to be enjoyed.

It will be remembered that perfect balance cannot be obtained in atwo-cycle engine arrangement and the overall magnitude of the vibrationremains the same, being governed in direction by the general design andmass of the unit and its components as aforementioned.

It has been found desirable, in a unit of the present type, to so designand engineer the unit that the resultant of the shaking forces would liein the fore-and-aft direction rather than in the up-and-down direction.Such an arrangement allows some of the shock to be absorbed by the logwhich the saw is cutting rather than being transferred to the hands of-an operator through the handle bar.

It is a further object of the invention, therefore, to so design thecomponents of the unit, together with its general mass, that the majordirection of the vibrating forces will occur along the longitudinalaxial plane of the saw and are minimized in the opposite plane.

Other objects and advantages of the invention will become apparent inthe courseof the following detailed description when viewed togetherwith the accompanying drawing in which:

FIG. 1 is a top plan view of a wood cutting saw made in accordance withthe teachings of the present invention.

FIG. 2 is a side elevational view of the saw illustrated in FIG. 1.

FIG. 3 is a detailed view of the actual reciprocating cutting bladeremoved from its stationary guide.

FIG. 4 is a detailed sectional view taken along line 4-4 of FIG. 2, butwith the reciprocating blade removed.

FIG. 5 is a cross-sectional view taken along lines 5-5 of FIG. 2.

FIG. 6 is a side elevational view pictorially illustrating the maindrive and balancing mechanism of the saw.

FIG. 7 is a pictorial diagram of the gear train and balancing featuresof the saw; and,

speed helps to reduce both the vibration and also the wear on FIG. 8 isa broken, isometric view illustrating the reciprocating mechanismshowing its' offset position with respect-to the main drive mechanism ofthe saw.

In FIG. l'the saw is shown in a top or plan view with a'blade 10extended from the front end of the saw and lying on a plane not onlythrough the central axis of the saw, but also through the approximatecenter of gravity.

FIG. 2 shows the guide 10 as mounted to the body portion of the saw bymeans of screws 12. The bottom edge of the guide 10 is providedwith aslot 13 suitable for receiving the cutting blade 11.

In FIG. 3 the cutting blade 11, as illustrated in this side elevationalview, is provided with cutting teeth 14 of the configuration shown,,thetop edge 15 of the blade being of a thickness suitable for being snuglyreceived in the slot 13 of the guide bar 10. In theguide bar 10 there isa pin 16 strategically located so as to be engageable with a slot 17formed on the forward end of the cutting blade 10. The inner end of theblade is affixed to a push rod 18 by means of which the blade 11 ismoved along the slotted guide bar 10 in a reciprocatory cutting action.

The present invention lies in the components and their particulararrangements more clearly shown by reference to FIGS. 6, 7 and 8. Here,numeral 19 designates the conventional engine crankshaft componentrotatably journaled on bearings 20. The crankshaft 19 is rotated in theusual manner by the conventional piston 21 and its correspondingconnecting rod 22. At one end of the crankshaft 19 is a magneto flywheel23 and at the other end is a centrifugally operated clutch 24.Associated with the clutch 24 is a clutch drum 25 with an integrallyformed pinion gear 26 adapted for free rotation on the crankshaft 19.The clutch pinion 26 is the driving member of a three-gear gear train,the other members being an idler gear 27 and afinal driven gear 28.

The final driven gear 28 is arranged to drive two connecting rods. Oneconnecting rod 29 connects the drive to a push rod 30 which, in turn, isaffixed to the cutting blade 11. The other rod 31 connects the drivengear 28 to a weight 32 adapted for movement along a track 33. The crosssection as shown in FIG. 5 will more clearly illustrate thesearrangements.

By reference to FIG. 6 it can be seen that as the reciprocatt ing blademoves in one direction of travel, as at B, the counby the fore-and-aftmovement of the blade as pointed out in the beginning of thisspecification. In the present instance, the counterweight 32 iscalculated to not only counterbalance the vibrating action of thecutting blade and its attendant components, but also to give directionto the overall shaking forces of the unit so that the major amplitude ofvibration will be in the fore-and-aft plane of the unit. Thus, when theblade is put to use in a cut, the log or other object being cut, willhelp absorb a portion of the mass vibration without the same beingtransferred to the operator's hands through the handlebars.

As seen by reference to FIG. 7, the planes of operation of the cuttingblade and the counterweight system lie adjacent each other through theapproximate center of the units mass and center of gravity. Hence therotating couple produced upon running the engine is reduced to aminimum. Moreover, the number of teeth on the driven gear 28 is twicethe number of'those on the driving pinion 26, so that the blade 11 willbe driven at one-half the speed of the engine. This reduction in thecomponent parts.

The invention is believed to be an advancement over the lar embodiment,it is to be understood that this has been by a way of example only, andthat changes in the size and shape of the various components could bemade without departing from the spirit and scope of the invention asdefined by the following claims.

We claim:

E. In a gasoline enginedriven saw having a crankshaft and acentrifugaily operable clutch, a clutch drum associated with saidclutch, a driving pinion affixed to said clutch drum and operabletherewith upon actuation of said clutch, an intermediate gear enmeshedwith said pinion, a final driven gear enmeshed with said intermediategear, said final driven gear provided with two crankpins set laterallyat equidistant points from the axial centerline of said gear anddiametrically opposed to each other, and a pair of connecting rodsoperatively associated with said driven gear, one of said rodsoperatively connected to a cutting blade and the other of said rodsconnected to a counterbalancing weight.

2. In a gasoline engine driven saw provided with a crankshaft, acentrifugally operable clutch on said crankshaft, a clutch drumassociated with said clutch, a driving pinion affixed to said drum andoperable for rotation therewith upon actuation of said clutch, anintermediate gear enmeshed with said pinion, a final driven gearenmeshed with said intermediate gear, a push rod slidably journaled insaid saw, a cutting blade attached to said push rod, a connecting rodjoining said push rod and said final driven gear whereby said cuttingblade may be given reciprocatory movements upon rotation of said finaldriven gear, and a second connecting rod rotatably affixed at one endthereof to said final driven gear and at the other and to acounterbalancing weight.

3. In a gasoline engine driven saw having a crankshaft and acentrifugally operable clutch on said crankshaft, a gear trainassociated with said clutch, a cutting blade operatively associated withsaid gear train, means for inducing reciprocating movement to saidcutting blade upon rotation of the gears of said gear train, acounterbalancing weight slidably mounted in said saw and also adaptedfor slidable reciprocatory movements by said gear train, and means formoving said cutting blade mechanism and said siidable weight insimultaneous opposite directions of travel.

4. In a gasoline engine driven saw having a crankshaft and acentrifugally operable clutch upon said shaft, a gear train operable bysaid clutch, a cutting blade mechanism mounted for reciprocatorymovement on said saw, means on said gear train for impartingreciprocatory movement to said cutting blade mechanism, and acounterbalancing weight also on said saw and operatively associated withsaid gear train for reciprocatory movements thereof in simultaneousopposite directions to said cutting blade mechanism, both said cuttingblade mechanism and said counterbalancing weight being substantially onthe axial centerline of the general mass of said saw.

5. In combination, with a gasoline engine having a crankshaft and acentrifugally operated clutch, a gear train operatively responsive tothe actuation of said clutch, said gear train including a pinion gear onsaid clutch, an intermediate gear enmeshed with said pinion, and a finaldrive gear enmeshed with said intermediate gear; ll cutting bladeconnected to said final gear and arranged for reciprocatory movement inresponse to the rotation of said gear, said cutting blade being positiored on the central longitudinal axis through the engine, and acounterbalancing weight associated also with and responsive to therotation of said final drive gear, said counterbalancing v\ eight lyingimmediately adjacent the said longitudinal axis of said saw and in aplane parallel thereto.

